I have a 55 by 100 machine shop that I’ve used to store grain in for part of the year. It was built about 20 years ago and the roof was nailed on but the sides were screwed on. The roof has started to leak around the rails now the washers have perished. I don’t want to re roof it as the sheets are in near perfect shape. Tried pulling the nails to replace with screws but the metal get so dented nothing is going to seal anymore. Is there a product that can be applied over 5he nails that will seal them. Thought of tar or roofing cement but it going to look a crappy job. Any thoughts.